This application proposes Martin P. Szuba, M.D. for a Mentored Clinical Scientist Development Award at the University of Pennsylvania. The aims of this program include: 1) to support his development into an independent research scientist 2) to support and enhance the applicant's development as an investigator in sleep and chronobiology in the elderly; 3) to develop him for a faculty leadership role in mood disorders at Penn; and 4) to enhance the study of late-life mood disorders at Penn, using a chronobiologic approach. These aims will be structured around a four-part plan: 1) A program of formal academic courses and tutorials aimed at enhancing his research skills. 2) Research training, supervised by Drs. David Dinges and Ira Katz. This training will include supervised participation in three ongoing studies of the Center for Sleep and Respiratory Neurobiology and the Clinical Research Center (CRC) in Depression in the Aged: Medical- Psychiatric Co-Morbidity (I. Katz, PI). 3) Performance of a separate research project: The first systematic randomized, double-blind, placebo-controlled treatment trial of the effects of exogenous melatonin administration on sleep, mood, and circadian rhythms in depressed elderly subjects. The specific aims of the study include a thorough evaluation in elderly depressed subjects with insomnia of subjective, behavioral, and physiological indices of sleep, in the laboratory and at home, as well as recording of circadian physiology during an unmasking protocol (constant routine), prior to and following treatment with melatonin or placebo. 4)Preparation, as Principal Investigator, of an independent research grant application.